The present invention relates generally to a turbomachine; and more particularly to a system for increasing the efficiency of a turbomachine.
Some turbomachines, such as, but not limiting of, a gas turbine, may generally include, in serial flow arrangement, an inlet system for receiving and channeling an ambient airstream; a compressor which receives and compresses that airstream, a combusting system that mixes a fuel and the compressed airstream, ignites the mixture, and allows for the gaseous by-product to flow to a turbine section; which transfers energy from the gaseous by-product to an output power. Other components of the gas turbine may be used therein.
The power output of a gas turbine is directly proportional to, and limited by, the mass flowrate of compressed airstream exiting the compressor. The compressor has a fixed capacity for handling a volumetric flowrate of the airstream for a given rotational speed of the compressor. The mass flowrate of the airstream decreases with an increase in ambient temperature because the density of the air decreases when air temperature increases. Therefore, the efficiency and power output of the gas turbine decreases below the rated capacity at the ISO conditions with increases in ambient temperature above ISO conditions.
To generate additional power from an existing gas turbine, an inlet air conditioning system is commonly used. The air conditioning system increases the airstream density by lowering the temperature of the airstream. This increases the mass flowrate of air entering the compressor, resulting in increased efficiency and power output of the gas turbine. An air conditioning system may include, for example, but not limiting of, a chiller, an evaporative cooler, a spray cooler, or combinations thereof, located downstream of an inlet filter house within an inlet system of the gas turbine. Some air conditioning systems, however, add resistance to the airstream entering the compressor. This resistance is defined as a pressure drop in the inlet system and may be measured in inches of water column. Gas turbine efficiency and power output are a direct function of the inlet system pressure drop.
The higher the inlet system pressure drop, the lower the efficiency and power output of the turbine. Typical pressure drop values across the gas turbine inlet system for power generation varies from about two (2) to about five (5) inches of water column (about five to about 12.7 centimeters of water). This includes the pressure drop across the air conditioning system, which varies from about 0.5 inches to about 1.5 inches of water column (about 1.27 to about 3.8 centimeters of water). Depending on the size of the gas turbine frame, the value of this pressure drop affects the gas turbine output anywhere in the range of about one (1) to about five (5) megawatts at rated ISO conditions. This in turn may affect the turbine efficiency in the range of about 0.01% to about 0.3%. Every point of efficiency and power, however, is essential in the competitive business of power generation or the variety of other uses for mechanical drive gas turbines.
Operators of existing gas turbines, (that do not have an air conditioning system), may desire the additional power output and efficiency increases these systems provide. However, these operators may resist retrofitting the gas turbine for a few reasons including operational downtime and construction costs. Gas turbine operators greatly avoid shutting down the machines because of the associated loss in revenue. Also, the cost of retrofitting an inlet system can be exorbitant.
One retrofitting approach involves inserting the air conditioning system downstream of the inlet filter house. This approach requires extensive retrofitting, which involves separating the inlet filter house from the transition piece. Next, the inlet filter house is moved forward such that the air conditioning system is inserted between the transition piece and the inlet filter house. Another retrofitting approach involves replacing the existing inlet filter house with a new inlet filter house having an air conditioning system therein. The downtime, lost revenues, and construction costs prohibit operators from adding an air conditioning system.
For the foregoing reasons, there is a need for an air condition system for retrofitting an operating gas turbine. After installing, the system should reduce the inlet system pressure drop when not in operation. The system components should be installed without a need for extending the overall inlet system. The system should be capable of being installed with minimum disruption to gas turbine operation.